1. Field of the Invention
The invention relates to solvent type cleaners with quick breaking emulsion properties, for cold cleaning of metal surfaces, concrete structures, brickwork, etc. which have been soiled with dirty mineral oil residues, oily and greasy dust, tarry substances and the like.
The term "cold cleaning" is used herein to indicate cleaning at ambient temperature up to 50.degree.C, and includes mechanical spray-cleaning as well as immersion cleaning.
2. Description of the Prior Art
Cold-immersion cleaners and mechanical spray cleaners for defatting of objects, particularly metal surfaces, are known in the art. They normally comprise a solvent, particularly a hydrocarbon solvent, and a suitable emulsifying agent.
Solvent cleaners of this type are preferably used for cleaning heavily soiled automotive engines and moving parts, such as wheels. Cleaning is generally accomplished by spraying the objects with the cleaner composition, by which on account of its solvent and emulsifying action the fatty and sticky soil is softened and loosened from the solid surface. After a certain time the loosened oily dirt still remaining on the surface is flushed with a copious and powerful spray of water.
By this operation an oil-in-water emulsion is formed which should pass an oil separator before the waste water can be drained as effluent water into open waters.
In composing a cleaning agent of this type it is important not only to achieve effective cleaning, but also to have a composition which produces with the flush water an emulsion which is capable of breaking into a water phase and an oil phase in a sufficiently short time, otherwise very large and expensive oil separators are needed to fulfil the requirements as to capacity.
Waste water pollution nowadays has become a serious problem all over the world, and authorities of many countries prohibit disposal of mineral oil products into municipal sewage systems. In some countries legal regulations exist which "emulsion cleaners" must comply with.
Many known solvent type cleaners do not produce a sufficiently quick breaking emulsion, and are therefore disadvantageous in use.
In German patent application No. 1935510 a solvent type cleaner is disclosed comprising a hydrocarbon solvent and a nonionic emulsifying agent, consisting of a mixture of dinonylphenol condensed with 4-6 ethylene oxide and monononylphenol condensed with 4-6 ethylene oxide.
The disadvantage of this emulsifier mixture is that it should be used at a rather high level (3-15%) in order to achieve the desired effects. Moreover, use of this specific nonionic mixture at the above level may generate too much foam, which is undesirable and therefore an anti-foaming agent is generally required.